1. Field of the Invention
This invention relates to a process for injecting air and water into a landfill to create anaerobic decomposition conditions and thereafter decreasing the volume of the landfill, i.e., the landfill air space by aerobic decomposition of decomposable municipal solid waste. Following municipal solid waste aerobic decomposition, the landfill may be mined in order to remove recoverable materials such as metals, plastics, glass and useful humus material. More specifically, this invention is a process and a landfill that includes a novel arrangement of wells for injecting moisture and air into a municipal solid waste undergoing aerobic decomposition in order to efficiently aerobically decompose waste.
2. Description of the Prior Art
The concept of aerobically decomposing a landfill to prepare it for a landfill mining is well known in the prior art. For example, in the article by R. I. Stessel et al. “A Lysimeter Study of the Aerobic Landfill Concept”; Waste Management and Research 10:45-503 (1992) the authors describe a process whereby water and air are injected into municipal solid waste in order to aerobically decompose the waste. The article further discloses that following aerobic decomposition, the waste may be mined to remove recoverable materials. More specifically, the Stessel et al. article discloses the use of water including recycle leachate and air to aerobically decompose municipal solid waste at conditions including a moisture content of from about 50 to about 80%.
A similar article by R. J. Murphy et al. “Aerobic Degradation of Municipal Solid Waste” For Presentation at 85th Annual Meeting and Exhibition, Kansas City, Mo. (Jun. 21-25, 1992) discloses aerobic decomposition studies performed on municipal solid waste at conditions including a temperature of from 30 to 89.4° C. (85-192° F.) an average moisture weight range of from 20 to 50% which was increased by leachate and water addition to a range of from 50 to 70%. The Murphy et al. paper also discloses that the aerobically treated municipal solid waste can be mined in order to recover the useful solid portions thereby allowing reuse of the mined landfill area.
Many issued U.S. patents also disclose process that employ aerobic decomposition processes. For example, U.S. Pat. No. 5,324,138 discloses an in-situ process for increasing the capacity of a municipal solid waste landfill using addition of moisture, lime, and physical disturbance to increase aerobic activity.
U.S. Pat. No. 5,356,452 discloses a process for recovering reusable materials subsequent to waste decomposition in an enclosed cell.
U.S. Pat. No. 5,265,979 discloses a high-efficiency waste placement and disposal method for solid waste in a landfill by reducing the size of the solid waste, adjusting the moisture, forming a waste pile, covering the waste pile, and compacting the waste pile. The disclosed method relies on slow anaerobic waste decomposition.
U.S. Pat. No. 5,702,499 discloses a batch process for the conversion of organic solid waste material through thermophilic aerobic digestion via mixing and moisture control.
U.S. Pat. No. 5,049,486 discloses a temperature monitoring method and apparatus for monitoring the temperature within a mass of organic matter moved through a composting vessel.
U.S. Pat. No. 4,077,847 discloses a system for segregating solid waste into ferrous metal, inorganic and organic fractions.
U.S. Pat. No. 4,410,142 discloses a method and an apparatus for composting waste using mixing and aeration.
U.S. Pat. No. 4,551,243 discloses a method to reduce the accumulation of undesirable solid material within an anaerobic digester.
U.S. Pat. No. 5,632,798 discloses a method for aerobic composition of organic waste material using high-flow aeration.
U.S. Pat. No. 5,584,904 discloses a process for reducing solid waste via shredding, anaerobic decomposition, aerobic decomposition, separation of the inorganic and organic waste, reduction of the plastic with solvents, and reduction of the metals with acids.
The prior art describes many methods and apparatus for decomposing municipal solid waste under aerobic or anaerobic conditions and/or mining aerobically or anaerobically decomposed landfills. There, however, remains a need for methods and landfill structures that enhance the delivery of water and air throughout a municipal solid waste a landfill in order to accelerate and control the aerobic decomposition of municipal solid waste.